Modulating arrangement for transmitter tubes



July 19, 1932. URTEL 1,868,033

MODULATING ARRANGEMENT FOR TRANSMITTER TUBES Fil ed Jan. 24, 1929 RES/STANCE anvzwtoz RUDOLF URTEL Patented July 19, 1932 UNITED STATES PArEnr carton] RUDOLF URTEL, F BERLIN, GERIEANY, ASSIGNOR TO TELEFUNKEN G-ESELLSCHAFT FU'R D'RAHTLOSE TELEGRAEHIE 331'. 18. IL, 013 BERLIN, GERMANY, A. CORPORATION OF GERMANY MODULATING- ARRANGEMENT FOR TRANSMITTER TUBES Application filed January 24, 1929, Serial No.

The present invention is concerned with a modulation system in which a so called modulator tube is made to control a transmitter circuit.

The main object of the invention is to dispense with the separate potential sources usually employed in such circuits.

Other objects of the invention will appear from time to time in the following detailed description of the invention when read in connection with the drawing in which Figure 1 illustrates diagrammatically a modulating arrangement utilizing a grid batter li igure 2 shows a similar system except that in accordance with the invention a resistance device replaces the grid battery;

Figure 3 shows diagrammatically a means of replacing the filament current source;

Figure 4 further illustrates means for furnishing the necessary negative bias for the modulator tube; and

Figure 5 illustrates all the above steps and also the means for obtaining the necessary potential for the microphone circuit.

In the drawing, Figures 1 to 5, inclusive, 2 represents a modulator tube connected across the grid filament circuit of a transmitter tube 1 which circuit also includes the resistance 3 and grid condenser 4 in parallel. Coil is arranged in series with the parallel branches named said coil serving to prevent the high frequency energy from the high frequency transmitter from afiecting the modulation circuit. It is seen therefore, that in saidv arrangement a supplementary direct current flows through the grid resistance 3 of the transmitter tube 1. In the case of Figure 1 the direct current is obtained through the agency of battery 5.

The purpose of tube 2 is for modulating the carrier wave according to the signals desired to be transmitted; that is, when the tube 2 is acted upon by the voice or any other agency,

a variation of the direct current takes place with the result that there occurs a fall of potential across resistance 3 which in turn, will afiect the transmitter tube to a suificient extent that the carrier is modulated. Resistance 3 also serves the purpose of furnishing the intensity of the filament 334,700, and in Germany February 13, 1928.

biasing means for the transmitter tube 1. Tube 2 and source 5 in Figure 1 are usually connected in the opposite sequence in order that the filaments of the transmitter Valve and the tube 2 may be supplied from one and 1'1- the same source of current.

In Figure 2, battery 5 is eliminated, the

the plate current through the filament of tube 2. Rheostat 7 is utilized for regulating the current. I In Figure 4:, a further fall of potential across a resistance 8 is employed to obtain a negative bias for the modulator tube 2. In said figure the circuithas been shown as including a portion ofthe microphone circuit 12.

Figure 5 illustrates the completed diagram; 13 is the microphone, 9 a resistance for obtaining the necessary potential required for the microphone circuit. As is evident from the drawing, the different resistances 6, 7, 8 and 9 may be combined into one large resistance with the necessary portions tapped off as shown. It is a good plan to have all the taps variable so that each section may be individually adjusted to any desired value.

The idea here disclosed while not limitedto any particular use is particularly advantageous in the case of small transmitter cirall connected electrically in series, one of said resistances being variab-ly shunted across the cathode of said space discharge device, an other thereof comprising a portion of said input circuit, and another a portion of said output circuit, and means comprising a translating device shunted across another of said resistances and coupled to said space discharge device input ior varying the impedance of said modulator space discharge device.

2. A radio system comprising a vacuum tube transmitter having grid and anode circuits, said anode circuit including a potential source and a resistance in series, a modulator tube connected in said grid circuit and adapted to control the transmitter tube grid bias, means comprising a microphone circuit shunted across a portion of said resistance for varying the impedance of said modulator tube and means for connecting the cathode of said modulator tube across another portion of said resistance.

3. A thermionic discharge device comprising a cathode, an anode and a control electrode, a circuit connecting said anode and cathode including a source of current and a resistance in series, a second circuit connecting said control electrode and cathode, said second named circuit comprising a space current device and a portion of said resistance in series and means shunted across another portion of said resistance for controlling the value of the space current through said space current device.

4. A thermionic discharge device comprising a cathode, an anode and a control electrode, a circuit connecting said anode and cathode including a source of current and a resistance in series, a second circuit connecting said control electrode and cathode, comprising a space discharge device, having a cathode, and a portion of said resistance in series, said last named cathode being shunted across another portion of said resistance and means shunted across still another portion of said resistance for varying the impedance of said space discharge device.

5. A thermionic discharge device comprising a cathode, an anode and a control electrode, a circuit connecting said anode and cathode including a source of current and a resistance in series, a second circuit connectlng said control electrode and cathode comprising a space discharge device, having an input circuit and a cathode, and a portion of said resistance in series, said cathode "being shunted across a portion of said first named resistance, said input circuit being shunted across, another portion of said resistance and means shunted across still another portion of said resistance for varying the impedance of said space discharge device.

6. In a transmitter circuit, an electron discharge device having an anode, a cathode and a control electrode, said cathode and con trol electrode being subjected to high frequency undulatory electrical potentials, a modulation circuit comprising a space discharge device connected across the control electrode and cathode of said electron discharge device, said last mentioned space discharge device having an anode, a cathode and a control electrode, a source of potential, an impedance in series With said source, means for establishing connections between said impedance and said control electrode cathode and anode of said space discharge device whereby said space discharge device is completely energized from said impedance, and, means for varying the potential on the control electrode of said space discharge device in order to vary the high frequency output of said first mentioned electron discharge device.

RUDOLF URTEL.

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